Semiconductor devices can be broadly categorized into two types: digital and analog. Analog devices may directly measure and/or manipulate the precise electrical properties (e.g., voltages) of real-world signals. For example, a touch sensor may detect objects in contact with and/or proximate to an input surface based on changes in a sensing signal (or electric field) measured at the input surface. The sensor may measure the exact amplitude of the sensing signal to determine the proximity of the object to the input surface. In contrast, digital devices tend to be more concerned with the presence or absence of a signal, rather than the precise amplitude of the signal. For example, a display driver may process image data to determine which pixels of a corresponding display panel should be turned “on” and which pixels should be turned “off.”
The manufacture of integrated circuit (IC) devices involves a wafer fabrication process in which circuit components (e.g., resistors, diodes, transistors, etc.) and their interconnections are formed on a single wafer of silicon (or other semiconductor substrate). The size and number of circuit components that can be fabricated on a single wafer of silicon is determined by the process node used during the fabrication process. For example, a smaller process node may produce smaller circuit components that are faster and more power-efficient. Because analog devices have greater precision and sensitivity requirements, their circuit components tend to be larger and consume more power than similar circuitry used in digital devices. Thus, the process node used to manufacture the wafer may be optimized for the type of device. For example, larger process nodes may be used to manufacture analog devices whereas smaller process nodes may be used to manufacture digital devices.
Some IC devices involve a mix of both analog and digital circuitry (e.g., “mixed-signal” devices). For example, an integrated controller that performs the functions of a touch sensor and a display driver may require analog circuitry for sensing and digital circuitry for display. However, as described above, each of the circuit components on a silicon wafer is fabricated using the same process node. Thus, when manufacturing mixed-signal devices, the analog circuitry is fabricated using a process node that is smaller than necessary (e.g., incurring significantly higher manufacturing costs) or the digital circuitry is fabricated using a process node that is larger than necessary (e.g., producing larger and less-efficient circuitry). It is therefore desirable to develop a mixed-signal device that can be manufactured with circuitry optimized for digital and analog applications without incurring unnecessarily high manufacturing costs.